variable-sized-arrays.cpp

#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    int n, q;
    
    cin >> n >> q;
    
    vector<vector<int>> array(n);
    
    for (int i = 0; i < n; i++) {
        int k;
		cin >> k;

		array[i].resize(k);
		for (int j = 0; j < k; j++)
			cin >> array[i][j];
    }
    
    for (int i = 0; i < q; i++) {
        int row, col;
        cin >> row >> col;
        cout << array[row][col] << endl;
    }
    
    return 0;
}